29 May 2007
President Musa Yar’Adua was inaugurated as President of Nigeria, after the April 2007 elections.   President Thabo Mbeki visited Nigeria for the inauguration ceremony of President Musa Yar’Adua, where he offered to help improve Nigeria’s electoral system. President Yar’ Adua’s inauguration ceremony was successful despite his rivals’ disputing the April election’s results. His main rivals were MuhammadBuhari of the All Nigeria People's Party (ANPP) and Vice President Atiku Abubakar.
References

Makosa M.B. (2007),’ Incoming Nigerian President Faces Many Problems’, from OhMy News, 23 May, [online], Available at: english.ohmynews.com  [Accessed: 30 April 2014]|Yar'Adua, Umara, M., (2010), 'Umaru Musa Yar'Adua biography', from Biography, 3 June, [online], Available at www.biography.com [Accessed: 03 June 2014]